What heads came on those? 088? SRP/JE pistons seem to be areal good bang for the buck. Just punch in 4.5” bore on the Summit site and party on from there.

Another issue no one has touched on is cam has nothing to do with exhaust cracking. If it cracks you're gonna fill with water. Reversion is due to overlap amongst other things generally in idle speeds.

I have a 2013 GM Perf. Marine long block with 300 hours that I just pulled. It is tip top and untouched other than comp ultra pro magnum rockers push rods. If you think you are interested I will send pics.